import json
import sys

def extract_hosts_to_file(json_data, output_filename="hosts.txt"):
    """Extracts hosts from a JSON object and writes them to a file.

    Args:
        json_data: The JSON object containing the hosts.
        output_filename: The name of the output text file (default: hosts.txt).
    """
    try:
        with open(output_filename, 'w') as outfile:
            for host in json_data.get("hosts", []):
                outfile.write(host.strip() + '\n')

    except (IOError, json.JSONDecodeError) as e:
        print(f"An error occurred: {e}")


if __name__ == "__main__":
    if len(sys.argv) > 1:
        json_filename = sys.argv[1]
        try:
            with open(json_filename, 'r') as f:
                json_data = json.load(f)
        except FileNotFoundError:
            print(f"Error: File '{json_filename}' not found.")
            sys.exit(1)
        except json.JSONDecodeError:
            print(f"Error: Invalid JSON format in '{json_filename}'.")
            sys.exit(1)

        if len(sys.argv) > 2:
            output_filename = sys.argv[2]
            extract_hosts_to_file(json_data, output_filename)
            print(f"Hosts extracted to '{output_filename}'") 
        else:
            extract_hosts_to_file(json_data)
            print("Hosts extracted to 'hosts.txt'")


    else:
        print("Usage: python script_name.py <json_filename> <output_filename>(optional)")
        default_json = {"hosts": []}
        extract_hosts_to_file(default_json)
        print("Hosts (from default JSON) extracted to 'hosts.txt'")